EV battery life extended by feeding energy back into the grid

Researchers at the University of Warwick have demonstrated a new "smart grid" system whereby energy from idle electric vehicle (EV) batteries could by pumped back into the grid to power large buildings, while still leaving enough power to complete the vehicle's daily journeys. The study also demonstrated that this approach could actually increase the overall longevity of the vehicle's lithium-ion battery.

This new research paves the way for vehicle-to-grid (V2G) technology that cleverly uses parked EVs to support localized power grids. The team developed a "smart grid" algorithm that can calculate how much energy an individual vehicle requires for its daily journey and how much energy can be safely taken from it and fed back into the grid.

The initial model calculated that a large building at the University of Warwick could be powered by the current number of EVs already parked on the campus. On a daily commute that consumes between 21 and 38 percent of a battery's capacity, the simulation estimated that feeding 40 and 48 percent of the battery's charge back into the grid could cut the inevitable capacity fade and power fade of the battery by around 6 and 3 percent, respectively, over a three-month period.

So not only did extracting this power not damage the batteries, but it actually improved their overall longevity. Analyzing some of the more advanced, commercially available EV batteries, the study claims that battery pack capacity fade can be reduced by up to 9 percent, and power fade by up to 12 percent through this V2G process.

"These findings reinforce the attractiveness of vehicle-to-grid technologies to automotive Original Equipment Manufacturers," says Dr Kotub Uddin, one of the lead authors of the research. "Not only is vehicle-to-grid an effective solution for grid support – and subsequently a tidy revenue stream – but we have shown that there is a real possibility of extending the lifetime of traction batteries in tandem."

The study looks forward to a win-win situation for electric vehicle owners in the future, where car batteries could have their life extended and offer a small revenue stream to the owners by supplying electricity to local grids.